Flat viscosity fluids and lubricating oils based on liquid crystal base stocks

ABSTRACT

Provided is a lubricant base stock, a lubricating oil including the lubricant base stock and a method for improving viscosity temperature performance or viscosity index of an engine or other mechanical component lubricated with the lubricating oil. The lubricant base stock includes one or more liquid crystals represented by the formula: 
       R1-(A) m -Y—(B) n —R2
 
     wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from 0 to 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH2-CH2-, —CH═CH—, —C≡C—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO2-, —CH2O—, —OCH2O—, —NO—, —ONO2, —COOH, —OH, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C., and 1 cSt to 12 cSt at 100° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Nos. 62/611,057, 62/611,072 and 62/611,081 all filed on Dec. 28, 2017, the entire contents of which are incorporated herein by reference.

FIELD

This disclosure relates to lubricant base stocks and lubricating oils having “flat viscosity” temperature performance based on use of phase change materials such as liquid crystal molecules. This disclosure relates to methods for improving viscosity temperature performance or viscosity index in an engine or other mechanical component lubricated with a lubricating oil containing at least one lubricating oil base stock having one or more liquid crystal molecules.

BACKGROUND

The viscosity of a lubricant base stock generally decreases as the temperature is increased. This viscosity decrease is undesirable because lower viscosity lubricants lead to more asperity-asperity interactions in the tribological contact compared to high viscosity lubricants. The sensitivity of a lubricant's viscosity to changes in temperature is characterized by its Viscosity Index (VI) with high VIs indicative of relative temperature insensitivity.

A major challenge in engine oil formulation is the development flat viscosity temperature performance for an engine lubricant so that it can be used both at low temperature and high temperature. Traditionally this performance can be achieved with appropriate polymeric viscosity index improvers or modifiers. Viscosity modifiers provide lubricants with high and low temperature operability. These additives provide the required film thickness to protect the bearing and moving parts within the equipment at elevated temperatures and acceptable viscosity at low temperatures.

However, there is a need for new and improved lubricating oil base stocks which can be incorporated into lubricating oils to provide improved viscosity performance at both low temperatures and high temperatures and provide a higher viscosity index.

SUMMARY

This disclosure relates to lubricant base stocks and lubricating oils including one or more liquid crystals for improving viscosity temperature performance or viscosity index.

More particularly, this disclosure relates to a lubricant base stock comprising one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445.

This disclosure also relates to a lubricating oil comprising a lubricant base stock including one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH, or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally one or more viscosity modifiers.

The disclosure still further more relates to a method for improving viscosity temperature performance or viscosity index of a lubricating oil used in an engine or other mechanical component comprising the steps of: providing a lubricating oil as a formulated oil to an engine or other mechanical component, said formulated oil having a composition comprising at least one lubricating oil base stock including one or more liquid crystals represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally one or more viscosity modifiers; and measuring viscosity temperature performance or viscosity index of the engine or other mechanical component lubricated with the lubricating oil; and wherein the viscosity temperature performance or viscosity index is improved as compared to viscosity temperature performance or viscosity index achieved using a comparable lubricating oil not including the lubricating oil base stock comprising the one or more liquid crystals.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustrative liquid crystal base oil in accordance with Example 1 of this disclosure.

FIG. 2 shows viscosity and viscosity index (VI) of liquid crystal base stock of Example 1 of this disclosure.

FIGS. 3A and 3B show Differential Scanning calorimetry (DSC) data for the L1 liquid crystal of Example 1, wherein FIG. 3A is a DSC heating scan and FIG. 3B is a DSC cooling scan.

FIG. 4 shows a plot of viscosity versus temperature with the viscosity increase occurring at a temperature of around 52° C.

FIG. 5 shows an illustrative liquid crystal base oil in accordance with Example 2 of this disclosure.

FIGS. 6A and 6B show DSC data for the L2 liquid crystal of Example 2, wherein FIG. 6A is a DSC heating scan and FIG. 6B is a DSC cooling scan.

FIG. 7 present viscosity as a function of temperature for the L2 liquid crystal of Example 2.

FIG. 8 shows the impact of shear on the alignment of molecules in the liquid crystal phase.

FIG. 9 shows the impact of shear on the alignment of molecules in the liquid crystal phase under oscillatory shear conditions.

FIG. 10 shows illustrative inventive liquid crystal base stocks in accordance with Examples 3 to 6 of this disclosure.

FIG. 11 shows phase transition temperatures of the liquid crystals of Examples 1 to 6 of this disclosure.

DETAILED DESCRIPTION Definitions

“About” or “approximately.” All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

“Liquid crystal” fluids mean highly anisotropic fluids that exist between the boundaries of the solid and conventional isotropic liquid phase. The phase is a result of long-range orientational ordering among constituent molecules that occurs within certain ranges or temperature in melts and solutions of many organic compounds. The various liquid crystal phases may be characterized by the type of ordering. Among these are namely nematic, smectic or discotic phases.

“Smectic liquid crystals” refer to hydrocarbon molecules that are arranged in layers, with the long molecular axes approximately perpendicular to the laminar planes. The only long range order extends along this axis, with the result that individual layers can slip over each other (soap-like in nature). A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

“Major amount” as it relates to components included within the lubricating oils of the specification and the claims means greater than or equal to 50 wt. %, or greater than or equal to 60 wt. %, or greater than or equal to 70 wt. %, or greater than or equal to 80 wt. %, or greater than or equal to 90 wt. % based on the total weight of the lubricating oil.

“Minor amount” as it relates to components included within the lubricating oils of the specification and the claims means less than 50 wt. %, or less than or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater than or equal to 20 wt. %, or less than or equal to 10 wt. %, or less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or less than or equal to 1 wt. %, based on the total weight of the lubricating oil.

“Essentially free” as it relates to components included within the lubricating oils of the specification and the claims means that the particular component is at 0 weight % within the lubricating oil, or alternatively is at impurity type levels within the lubricating oil (less than 100 ppm, or less than 20 ppm, or less than 10 ppm, or less than 1 ppm).

“Flat viscosity” temperature performance as it relates to the lubricant base stocks and lubricating oils disclosed herein mean that the viscosity does not vary as a function of temperature over a temperature range from 20 to 100 deg. C.

“Other lubricating oil additives” as used in the specification and the claims means other lubricating oil additives that are not specifically recited in the particular section of the specification or the claims. For example, other lubricating oil additives may include, but are not limited to, antioxidants, detergents, dispersants, antiwear additives, corrosion inhibitors, viscosity modifiers, metal passivators, pour point depressants, seal compatibility agents, antifoam agents, extreme pressure agents, friction modifiers and combinations thereof.

“Other mechanical component” as used in the specification and the claims means an electric vehicle component, a hybrid vehicle component, a power train, a driveline, a transmission, a gear, a gear train, a gear set, a compressor, a pump, a hydraulic system, a bearing, a bushing, a turbine, a piston, a piston ring, a cylinder liner, a cylinder, a cam, a tappet, a lifter, a gear, a valve, or a bearing including a journal, a roller, a tapered, a needle, and a ball bearing.

“Hydrocarbon” refers to a compound consisting of carbon atoms and hydrogen atoms.

“Alkane” refers to a hydrocarbon that is completely saturated. An alkane can be linear, branched, cyclic, or substituted cyclic.

“Olefin” refers to a non-aromatic hydrocarbon comprising one or more carbon-carbon double bond in the molecular structure thereof.

“Mono-olefin” refers to an olefin comprising a single carbon-carbon double bond.

“Cn” group or compound refers to a group or a compound comprising carbon atoms at total number thereof of n. Thus, “Cm-Cn” group or compound refers to a group or compound comprising carbon atoms at a total number thereof in the range from m to n. Thus, a C1-C50 alkyl group refers to an alkyl group comprising carbon atoms at a total number thereof in the range from 1 to 50.

“Carbon backbone” refers to the longest straight carbon chain in the molecule of the compound or the group in question. “Branch” refer to any substituted or unsubstituted hydrocarbyl group connected to the carbon backbone. A carbon atom on the carbon backbone connected to a branch is called a “branched carbon.”

“SAE” refers to SAE International, formerly known as Society of Automotive Engineers, which is a professional organization that sets standards for internal combustion engine lubricating oils.

“SAE J300” refers to the viscosity grade classification system of engine lubricating oils established by SAE, which defines the limits of the classifications in rheological terms only.

“Base stock” or “base oil” interchangeably refers to an oil that can be used as a component of lubricating oils, heat transfer oils, hydraulic oils, grease products, and the like.

“Lubricating oil” or “lubricant” interchangeably refers to a substance that can be introduced between two or more surfaces to reduce the level of friction between two adjacent surfaces moving relative to each other. A lubricant base stock is a material, typically a fluid at various levels of viscosity at the operating temperature of the lubricant, used to formulate a lubricant by admixing with other components. Non-limiting examples of base stocks suitable in lubricants include API Group I, Group II, Group III, Group IV, and Group V base stocks. PAOs, particularly hydrogenated PAOs, have recently found wide use in lubricants as a Group IV base stock, and are particularly preferred. If one base stock is designated as a primary base stock in the lubricant, additional base stocks may be called a co-base stock.

All kinematic viscosity values in this disclosure are as determined pursuant to ASTM D445. Kinematic viscosity at 100° C. is reported herein as KV100, and kinematic viscosity at 40° C. is reported herein as KV40. Unit of all KV100 and KV40 values herein is cSt unless otherwise specified.

All viscosity index (“VI”) values in this disclosure are as determined pursuant to ASTM D2270.

All Noack volatility (“NV”) values in this disclosure are as determined pursuant to ASTM D5800 unless specified otherwise. Unit of all NV values is wt %, unless otherwise specified.

All pour point values in this disclosure are as determined pursuant to ASTM D5950 or D97.

All CCS viscosity (“CCSV”) values in this disclosure are as determined pursuant to ASTM 5293. Unit of all CCSV values herein is millipascal second (mPa·s), which is equivalent to centipoise), unless specified otherwise. All CCSV values are measured at a temperature of interest to the lubricating oil formulation or oil composition in question. Thus, for the purpose of designing and fabricating engine oil formulations, the temperature of interest is the temperature at which the SAE J300 imposes a minimal CCSV.

All percentages in describing chemical compositions herein are by weight unless specified otherwise. “Wt. %” means percent by weight.

Overview of Lubricant Base Stocks and Lubricating Oils Disclosed Herein

This disclosure relates to lubricant base stocks and lubricating oils that have “flat viscosity” temperature performance based on use of phase change materials such as liquid crystal molecules. This disclosure also relates to lubricant base stocks and lubricating oils that have high viscosity index “flat viscosity” temperature performance based on use of phase change materials such as liquid crystal molecules along with polymer viscosity index improvers. The base stocks are useful in lubricating oils for internal combustion engines, hybrid engines, electrical vehicle components and other mechanical components lubricated with a lubricating oil. Also, this disclosure relates to method for improving viscosity temperature performance or viscosity index in an engine or other mechanical component lubricated with a lubricating oil, by using a lubricating oil containing at least one lubricating oil base stock having one or more liquid crystal molecules.

Liquid crystal (LC) molecules, due to their ability to align along flow directions exhibit lower traction coefficients in tribological contacts compared to conventional lubricants. For this reason, they are promising candidates for a new class of lubricant base stocks.

Under certain conditions of temperature and pressure, liquid crystalline molecules are capable of forming phases with orientational order. However, unlike solid crystals, they do not possess strict positional order. This ordering or preferred directionality of the molecules leads to domains of anisotropy over large length scales, which can be many orders of magnitude larger than molecular size. Liquid crystals (LCs) have well-defined directionality on average, described by a vector known as the director. The intermolecular interactions between molecules are weak enough for thermally induced fluctuations to perturb the molecules, giving the system liquid-like character and enabling it to flow under applied stress. The tendency for liquid crystals to exhibit orientational alignment provides advantageous properties as lubricant base stocks, either as co-base stocks or when used pure. The alignment of the molecules causes them to slide past each other easier than purely isotropic molecules, leading to lower friction. The anisotropic nature of LCs make them particularly suited to lubrication applications; for example, LCs can exhibit increased load bearing capabilities under normal loading conditions, and at the same time low friction when sheared in the direction of alignment.

Despite the extensive work done in establishing structure property relationships and understanding phase behavior, the behavior of LCs under the high pressures or shear rates in a tribological contact remains poorly understood and is partially the subject of this disclosure.

Lubricating Oil Base Stocks Containing Smectic Liquid Crystals

This application deals with use of liquid crystals as lubricant base stocks, performance additives, and “smart” materials for use in lubricating oils.

In accordance with this disclosure, liquid crystal base oils or base stocks are provided that offer a route to improve lubricant energy efficiency without reducing load-bearing capability. As compared to simple hydrocarbon fluids, the viscosity of the liquid crystal base oil or base stock does not need to be lowered to achieve improved traction. Also, in accordance with this disclosure, the use of flat viscosity temperature performance base stock comprised of liquid crystals such as liquid crystals are represented by the formula:

and combinations thereof of liquid crystals or analogs with differing R group side chains or differing core structure still containing two rings, at least one aromatic, with or without additional additives or base stocks present, to give “flat viscosity” temperature performance compared to non-liquid crystal hydrocarbon fluids of the same viscosities. The liquid crystal lubricants exhibit advantageous “flat viscosity” temperature performance or viscosity index from hydrocarbon-only fluids.

This disclosure relates in part to a lubricant base stock comprising one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, —CCO, —OH or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricant base stock has a kinematic viscosity of about 2 cSt to about 28 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 12 cSt at 100° C., as determined according to ASTM D445.

This disclosure also relates to lubricating oils including the lubricant base stock comprising one or more liquid crystals described in the previous paragraph wherein the lubricating oils have advantageous “flat viscosity” temperature performance or viscosity index. This disclosure also relates in part to a method for improving flat viscosity temperature performance or viscosity index, in an engine or other mechanical component lubricated with a lubricating oil, by using as the lubricating oil a formulated oil. The formulated oil has a composition comprising at least one lubricating oil base stock. The at least one lubricant base stock comprises one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, —COOH, —OH or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricating oil base stock has a kinematic viscosity of about 2 cSt to about 28 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of about 1 cSt to about 12 cSt at 100° C., as determined according to ASTM D445. Wear control is improved and energy efficiency is maintained or improved as compared to wear control and energy efficiency achieved using a lubricating oil containing a lubricant base stock other than the lubricant base stock comprising one or more liquid crystals disclosed herein.

Advantageous liquid crystals for use as lubricant base stocks and in lubricating oils of the instant disclosure are represented by the formula:

and combinations thereof.

It has been unexpectedly and surprisingly found that, in accordance with this disclosure, improvements in flat viscosity temperature performance and viscosity index in an engine or other mechanical component (as defined below) lubricated with a lubricating oil are obtained, when the lubricating oil contains at least one lubricating oil base stock comprised of one or more liquid crystals, and optionally a viscosity modifier (e.g., a polymer thickening agent). In particular, it has been unexpectedly and surprisingly found that, in accordance with this disclosure, with respect to the lubricating oil base stock comprised of one or more liquid crystals in flat viscosity temperature performance measurements of the lubricant base stock by viscosity and viscosity index measurements. Also, in particular, it may be useful to blend the lubricating oil base stock comprised of one or more liquid into a lubricating oil for improving viscosity temperature performance of the oil.

Liquid crystal (LC) molecules, due to their ability to align along flow directions exhibit lower traction coefficients in tribological contacts compared to conventional lubricants. For this reason, it has been discovered that they are advantageous as a new class of base stocks. It has been discovered that a LC with low viscosity (kV100=3:88 cSt) and low molecular weight (Mw=255 g/mol) exhibits surprisingly high viscosity index (VI) of 329. In contrast, a PAO of similar viscosity has a VI of 126. DSC and rheology measurements help explain the reason for the high VI values measured. It has been discovered that there is an increase in viscosity with increase in temperature because of a nematic to isotropic transition in the liquid crystal. The LC lubricant base stocks disclosed herein provide for using LCs as low traction, high VI lubricant basestocks. In addition, using a combination of LC molecules with appropriately selected phase transition temperatures enable the formulation of base stocks that have nearly constant viscosity with changes in temperature.

The base stock or lubricant that have flat viscosity temperature performance based on use of phase change materials such as liquid crystal molecules of this disclosure are comprised of liquid crystals such as for example, 4-((1s,4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate or analogs with differing R group side chains or differing core structure still containing two rings, at least one aromatic, with or without additional additives or base stocks present, to give flat viscosity temperature performance compared to non-liquid crystal hydrocarbon fluids of the same viscosities. The liquid crystal fluids disclosed herein optionally contain oxygen heteroatoms.

The lubricant base stocks of this disclosure comprise one or more liquid crystals. The one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, —COOH, —OH, or —C≡N; and m and n are independently 0, 1, 2 or 3. The lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C., as determined according to ASTM D445, and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445.

Other non-limiting LC lubricant base stocks of the instant disclosure are represented by the formula below.

In particular, illustrative advantageous liquid crystals useful in this disclosure include, for example, 4-((1s,4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate and mixtures thereof.

Other non-limiting exemplary liquid crystal fluid base stocks useful in this disclosure include, 4-pentylphenyl, 4-methylbenzoate, 4-pentylphenyl 4-ethylbenzoate, 4-pentylphenyl 4-propylbenzoate, 4-pentylphenyl 4-butylbenzoate, 4-pentylphenyl 4-(octyloxy)benzoate, 4-pentylphenyl 4-methoxybenzoate, 4-pentylphenyl 4-ethoxybenzoate, 4-pentylphenyl 4-propoxybenzoate, 4-pentylphenyl 4-butoxybenzoate, 4-pentylphenyl 4-pentoxybenzoate, and mixtures thereof.

The liquid crystal (LC) fluids of this disclosure haves a state of matter that is both fluid and anisotropic in nature—essentially these materials are not solids, which possess a highly ordered crystalline structure and lack ability of translation of molecules in any direction, and they are not liquids, which are characterized by their lack of order but intermolecular forces that overcome kinetic energy, keeping them in a condensed phase. Instead liquid crystals can be considered “partly ordered” in that in some direction(s) they may appear ordered, and in others they may appear disordered. These LC) fluids are therefore anisotropic in nature, and the amount of ordering seen depends on from which angle they are viewed. A smectic phase of a liquid crystal can possess two directions of order including one along the axis of molecular orientation, and the other along the traverse axis where molecules show layering.

The liquid crystal base stocks of this disclosure have a kinematic viscosity, according to ASTM standards, of about 2 cSt to about 28 cSt (or mm²/s) at 40° C. and preferably of about 2.5 cSt to about 25 cSt (or mm²/s) at 40° C., often more preferably from about 2.5 cSt to about 20 cSt at 40° C. Also, the liquid crystal base stocks have a kinematic viscosity, according to ASTM standards, of about 1 cSt to about 12 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 10.5 cSt (or mm²/s) at 100° C., often more preferably from about 2.5 cSt to about 10 cSt at 100° C.

The liquid crystal base stocks of this disclosure have a viscosity index of the lubricating oil base stock that is greater than −100, or greater than 0, or greater than 100, or greater than 150, or greater than 200, or greater than 250, or greater than 300 at 100° C. as determined according to ASTM D-2270 the viscosity index of the fluids is >−100, >0, >100, >200 or >300 cSt at 100° C. as determined according to ASTM D-2270.

The liquid crystal base stocks and mixtures thereof of this disclosure have a liquid crystal phase change or phase changes range from −50 to 150° C., or 0 to 100° C., or 20 to 90° C., or 20 to 30° C., or 44.6 to 60.4° C., or 42.4 to 60.4° C., or 66.7 to 85.9° C. as determined by DSC.

Preferably, the liquid crystal base oil constitutes the major component of the lubricating oil for the engine, or other mechanical component. With the lubricating oils disclosed herein, the liquid crystal base stock may be present in an amount ranging from about 5 to about 99 weight percent, or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the lubricating oil composition.

Mixtures of liquid crystal base stocks described above may also be used in the lubricating oils disclosed herein. Bi-modal, tri-modal, and additional combinations of mixtures of liquid crystal base stocks and optional inclusion of Group I, II, III, IV, and/or V base stocks may be used if desired. With mixtures of liquid crystal base oils and Group I, II, III, IV, and/or V base stocks, the liquid crystal base stock may be present is an amount ranging from about 5 to about 99 weight percent, or from about 10 to about 95 weight percent, preferably from about 50 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the lubricating oil composition. Preferably, with mixtures of liquid crystal base stocks and Group I, II, III, IV, and/or V base stocks, the liquid crystal base oil is present is an amount ranging from about 50 to about 99 weight percent, or from about 55 to about 95 weight percent, preferably from about 60 to about 99 weight percent or from about 70 to about 95 weight percent, and more preferably from about 85 to about 95 weight percent, based on the total weight of the lubricating oil composition.

The lubricating oils of this disclosure including liquid crystal base stocks may have a viscosity index of the lubricating oil that is greater than −100, or greater than 0, or greater than 100, or greater than 150, or greater than 200, or greater than 250, or greater than 300 at 100° C. as determined according to ASTM D-2270 the viscosity index of the fluids is >−100, >0, >100, >200 or >300 cSt at 100° C. as determined according to ASTM D-2270.

The liquid crystal base stocks and mixtures thereof of this disclosure have a liquid crystal phase change or phase changes range from −50 to 150° C., or 0 to 100° C., or 20 to 90° C., or 20 to 30° C., or 44.6 to 60.4° C., or 42.4 to 60.4° C., or 66.7 to 85.9° C. as determined by DSC.

Other non-limiting liquid crystal base stocks that may be used in the lubricating oils of the instant disclosure are shown below.

Cholesteryl benzoate, Cholesteric, mp 148-150.

1,4-Bis(decyloxy)benzene, Smectic, mp 66-70.

4-(heptyloxy)benzoic acid, Smectic, mp 146

4-(Undecyloxy)benzoic acid, mp 94-138C

4-Ethyl-4′-(trans-4-propylcyclohexyl)biphenyl Mesomorphic range 134-169° C.

4-(trans-4-Pentylcyclohexyl)benzonitrile LC Nematic, mp 30-55 C

4-(trans-4-Amylcyclohexyl)benzonitrile Mesomorphic range 27-57° C. (mp 30° C.).

1-(trans-4-Hexylcyclohexyl)-4-isothiocyanatobenzene LC Nematic, mp 30-55 C

4′-Octyl-4-biphenylcarbonitrile LC Nematic

4′-(Octyloxy)-4-biphenylcarbonitrile LC Nematic mp 51-770 The liquid crystals can have general structure shown below.

R is alkyl or alkoxy group

R is alkyl or alkoxy group.

In addition, mixtures of one or more of the LC base stocks disclosed above that may be used in lubricating oils.

The lubricating oils including liquid crystal base stocks disclosed herein may also optionally include one or more lubricant co-base stocks. Non-limiting exemplary co-base stocks that may be used in the lubricating oils include a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock and combinations thereof. The lubricant co-base stock may be included in the lubricating oil at from 1 to 45 wt %, or 5 to 40 wt %, or 10 to 35 wt %, or 15 to 30 wt %, or 20 to 25 wt % of the total weight of the lubricating oil composition.

The lubricating oils including liquid crystal base stocks disclosed herein may also optionally include one or more polymeric viscosity index improvers. In one form, the viscosity modifier comprises a polymer thickening agent. Non-limiting exemplary polymer thickening agents may include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, polyacrylates and combinations thereof. The one or more viscosity modifiers may be incorporated into the lubricating oil at from 0.1 to 20 wt %, or 0.3 to 15 wt %, or 0.5 to 10 wt %, or 1 to 9 wt %, or 3 to 7 wt %, or 4 to 6 wt % of the lubricating oil composition.

Uses of the Lubricating Oil Including Base Stocks Containing Liquid Crystals

Also provided herein is a method for improving viscosity temperature performance or viscosity index of a lubricating oil used in an engine or other mechanical component. The method includes the steps of: (i) providing a lubricating oil as a formulated oil to an engine or other mechanical component, said formulated oil having a composition comprising at least one lubricating oil base stock including one or more liquid crystals represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally including one or more viscosity modifiers; and (ii) measuring viscosity temperature performance or viscosity index of the engine or other mechanical component lubricated with the lubricating oil. The method provides a viscosity temperature performance or viscosity index that is improved as compared to viscosity temperature performance or viscosity index achieved using a comparable lubricating oil not including the lubricating oil base stock comprising the one or more liquid crystals.

The improvement in viscosity temperature performance or viscosity index relative to a comparable lubricating oil not including the lubricating oil base stock comprising the one or more liquid crystals is greater than 1%, or greater than 2%, or greater than 5%, or greater than 10%, or greater than 15%, or greater than 20%, or greater than 25%, or greater than 50%, or greater than 60%, or greater than 75%, or greater than 100%.

The lubricating oils including a lubricant base stock comprising one or more liquid crystals may be used for lubricating a wide range of mechanical components. Non-limiting exemplary mechanical components include an internal combustion engine, a hybrid engine, electric vehicle components, a power train, a driveline, a transmission, a gear, a gear train, a gear set, a compressor, a pump, a hydraulic system, a bearing, a bushing, a turbine, a piston, a piston ring, a cylinder liner, a cylinder, a cam, a tappet, a lifter, a gear, a valve, or a bearing including a journal, a roller, a tapered, a needle, or a ball bearing. One advantageous mechanical component for use of the lubricating oils disclosed herein is an internal composition engine because of the improvement in viscosity temperature performance and viscosity index.

When the lubricating oils including a lubricant base stock comprising one or more liquid crystals disclosed herein are used as an engine oil, they may be used as a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO). The engine oils include SAE viscosity grades selected from the group consisting of 0W-30, 5W-30, 0W-20, 5W-20, 0W-16, 5W-16, 0W-12, 5W-12, 0W-8, and 5W-8.

Optional Lubricating Oil Base Stocks and Co-Base Stocks

A wide range of optional lubricating base oils or base stocks are known in the art. Optional lubricating base oils or base stocks that are useful in the present disclosure as a co-base stock are natural oils, mineral oils and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between about 80 to 120 and contain greater than about 0.03% sulfur and/or less than about 90% saturates. Group II base stocks have a viscosity index of between about 80 to 120, and contain less than or equal to about 0.03% sulfur and greater than or equal to about 90% saturates. Group III stocks have a viscosity index greater than about 120 and contain less than or equal to about 0.03% sulfur and greater than about 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or >0.03% and ≥80 and <120 Group II ≥90 and ≤0.03% and ≥80 and <120 Group III ≥90 and ≤0.03% and ≥120 Group IV polyalphaolefins (PAO) Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks are also well known base stock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks are commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are known materials and generally available on a major commercial scale from suppliers such as ExxonMobil Chemical Company, Chevron Phillips Chemical Company, BP, and others, typically vary from about 250 to about 3,000, although PAO's may be made in viscosities up to about 150 cSt (100° C.). The PAOs are typically comprised of relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include, but are not limited to, C₂ to about C₃₂ alphaolefins with the C₈ to about C₁₆ alphaolefins, such as 1-octene, 1-decene, 1-dodecene and the like, being preferred. The preferred polyalphaolefins are poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures thereof and mixed olefin-derived polyolefins. However, the dimers of higher olefins in the range of C₁₂ to C₁₈ may be used to provide low viscosity base stocks of acceptably low volatility. Depending on the viscosity grade and the starting oligomer, the PAOs may be predominantly dimers, trimers and tetramers of the starting olefins, with minor amounts of the lower and/or higher oligomers, having a viscosity range of 1.5 cSt to 12 cSt. PAO fluids of particular use may include 3 cSt, 3.4 cSt, and/or 3.6 cSt and combinations thereof. Mixtures of PAO fluids having a viscosity range of 1.5 cSt to approximately 150 cSt or more may be used if desired. Unless indicated otherwise, all viscosities cited herein are measured at 100° C.

The PAO fluids may be conveniently made by the polymerization of an alphaolefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate. For example the methods disclosed by U.S. Pat. No. 4,149,178 or 3,382,291 may be conveniently used herein. Other descriptions of PAO synthesis are found in the following U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No. 4,218,330.

Other useful lubricant oil base stocks include wax isomerate base stocks and base oils, comprising hydroisomerized waxy stocks (e.g. waxy stocks such as gas oils, slack waxes, fuels hydrocracker bottoms, etc.), hydroisomerized Fischer-Tropsch waxes, Gas-to-Liquids (GTL) base stocks and base oils, and other wax isomerate hydroisomerized base stocks and base oils, or mixtures thereof. Fischer-Tropsch waxes, the high boiling point residues of Fischer-Tropsch synthesis, are highly paraffinic hydrocarbons with very low sulfur content. The hydroprocessing used for the production of such base stocks may use an amorphous hydrocracking/hydroisomerization catalyst, such as one of the specialized lube hydrocracking (LHDC) catalysts or a crystalline hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst. For example, one useful catalyst is ZSM-48 as described in U.S. Pat. No. 5,075,269, the disclosure of which is incorporated herein by reference in its entirety. Processes for making hydrocracked/hydroisomerized distillates and hydrocracked/hydroisomerized waxes are described, for example, in U.S. Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as in British Patent Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Each of the aforementioned patents is incorporated herein in their entirety. Particularly favorable processes are described in European Patent Application Nos. 464546 and 464547, also incorporated herein by reference. Processes using Fischer-Tropsch wax feeds are described in U.S. Pat. Nos. 4,594,172 and 4,943,672, the disclosures of which are incorporated herein by reference in their entirety.

Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized (wax isomerate) base oils be advantageously used in the instant disclosure, and may have useful kinematic viscosities at 100° C. of about 2 cSt to about 50 cSt, preferably about 2 cSt to about 30 cSt, more preferably about 3 cSt to about 25 cSt, as exemplified by GTL 4 with kinematic viscosity of about 4.0 cSt at 100° C. and a viscosity index of about 141. These Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized base oils may have useful pour points of about −20° C. or lower, and under some conditions may have advantageous pour points of about −25° C. or lower, with useful pour points of about −30° C. to about −40° C. or lower. Useful compositions of Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and wax-derived hydroisomerized base oils are recited in U.S. Pat. Nos. 6,080,301; 6,090,989, and 6,165,949 for example, and are incorporated herein in their entirety by reference.

The hydrocarbyl aromatics can be used as a base oil or base oil component and can be any hydrocarbyl molecule that contains at least about 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl biphenyls, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatic can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from about C₆ up to about C₆₀ with a range of about C₈ to about C₂₀ often being preferred. A mixture of hydrocarbyl groups is often preferred, and up to about three such substituents may be present. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least about 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 2 cSt to about 50 cSt are preferred, with viscosities of approximately 3 cSt to about 20 cSt often being more preferred for the hydrocarbyl aromatic component. In one embodiment, an alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene is used. Other alkylates of aromatics can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Alkylated naphthalene and analogues may also comprise compositions with isomeric distribution of alkylating groups on the alpha and beta carbon positions of the ring structure. Distribution of groups on the alpha and beta positions of a naphthalene ring may range from 100:1 to 1:100, more often 50:1 to 1:50 Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be about 2% to about 25%, preferably about 4% to about 20%, and more preferably about 4% to about 15%, depending on the application.

Alkylated aromatics such as the hydrocarbyl aromatics of the present disclosure may be produced by well-known Friedel-Crafts alkylation of aromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York, 1963. For example, an aromatic compound, such as benzene or naphthalene, is alkylated by an olefin, alkyl halide or alcohol in the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many homogeneous or heterogeneous, solid catalysts are known to one skilled in the art. The choice of catalyst depends on the reactivity of the starting materials and product quality requirements. For example, strong acids such as AlCl₃, BF₃, or HF may be used. In some cases, milder catalysts such as FeCl₃ or SnCl₄ are preferred. Newer alkylation technology uses zeolites or solid super acids.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols (such as the neopentyl polyols, e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol) with alkanoic acids containing at least about 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Suitable synthetic ester components include the esters of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids containing from about 5 to about 10 carbon atoms. These esters are widely available commercially, for example, the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company.

Also useful are esters derived from renewable material such as coconut, palm, rapeseed, soy, sunflower and the like. These esters may be monoesters, di-esters, polyol esters, complex esters, or mixtures thereof. These esters are widely available commercially, for example, the Mobil P-51 ester of ExxonMobil Chemical Company.

Engine oil formulations containing renewable esters are included in this disclosure. For such formulations, the renewable content of the ester is typically greater than about 70 weight percent, preferably more than about 80 weight percent and most preferably more than about 90 weight percent.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non-conventional or unconventional base stocks/base oils include one or more of a mixture of base stock(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate base stock(s) derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from about 2 mm²/s to about 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to about −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of about 80 to about 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than about 10 ppm, and more typically less than about 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorus and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

Optional base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

The optional base oil is typically is present in an amount ranging from about 6 to about 49 weight percent or from about 6 to about 45 weight percent, preferably from about 10 to about 49 weight percent or from about 20 to about 45 weight percent, and more preferably from about 25 to about 45 weight percent, based on the total weight of the composition. The optional base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricating oils for spark-ignited and compression-ignited engines. The optional base oil conveniently has a kinematic viscosity, according to ASTM standards, of about 2.5 cSt to about 18 cSt (or mm²/s) at 100° C. and preferably of about 2.5 cSt to about 12.5 cSt (or mm²/s) at 100° C., often more preferably from about 2.5 cSt to about 10 cSt. Mixtures of synthetic and natural base oils may be used if desired. Bi-modal, tri-modal, and additional combinations of mixtures of Group I, II, III, IV, and/or V base stocks may be used if desired.

Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to antiwear additives, dispersants, detergents, viscosity modifiers, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N J (1973); see also U.S. Pat. No. 7,704,930, the disclosure of which is incorporated herein in its entirety. These additives are commonly delivered with varying amounts of diluent oil that may range from 5 weight percent to 50 weight percent.

The additives useful in this disclosure do not have to be soluble in the lubricating oils. Insoluble additives in oil can be dispersed in the lubricating oils of this disclosure.

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the (poly)alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from about 1:1 to about 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500 or more. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from about 0.1 to about 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HNR₂ group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from about 500 to about 5000, or from about 1000 to about 3000, or about 1000 to about 2000, or a mixture of such hydrocarbylene groups, often with high terminal vinylic groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components.

Polymethacrylate or polyacrylate derivatives are another class of dispersants. These dispersants are typically prepared by reacting a nitrogen containing monomer and a methacrylic or acrylic acid esters containing 5-25 carbon atoms in the ester group. Representative examples are shown in U.S. Pat. Nos. 2,100,993, and 6,323,164. Polymethacrylate and polyacrylate dispersants are normally used as multifunctional viscosity modifiers. The lower molecular weight versions can be used as lubricant dispersants or fuel detergents.

Illustrative preferred dispersants useful in this disclosure include those derived from polyalkenyl-substituted mono- or dicarboxylic acid, anhydride or ester, which dispersant has a polyalkenyl moiety with a number average molecular weight of at least 900 and from greater than 1.3 to 1.7, preferably from greater than 1.3 to 1.6, most preferably from greater than 1.3 to 1.5, functional groups (mono- or dicarboxylic acid producing moieties) per polyalkenyl moiety (a medium functionality dispersant). Functionality (F) can be determined according to the following formula:

F=(SAP×M_(n))/((112,200×A.I.)−(SAP×98))

wherein SAP is the saponification number (i.e., the number of milligrams of KOH consumed in the complete neutralization of the acid groups in one gram of the succinic-containing reaction product, as determined according to ASTM D94); M_(n) is the number average molecular weight of the starting olefin polymer; and A.I. is the percent active ingredient of the succinic-containing reaction product (the remainder being unreacted olefin polymer, succinic anhydride and diluent).

The polyalkenyl moiety of the dispersant may have a number average molecular weight of at least 900, suitably at least 1500, preferably between 1800 and 3000, such as between 2000 and 2800, more preferably from about 2100 to 2500, and most preferably from about 2200 to about 2400. The molecular weight of a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl moiety. This is because the precise molecular weight range of the dispersant depends on numerous parameters including the type of polymer used to derive the dispersant, the number of functional groups, and the type of nucleophilic group employed.

Polymer molecular weight, specifically M_(n), can be determined by various known techniques. One convenient method is gel permeation chromatography (GPC), which additionally provides molecular weight distribution information (see W. W. Yau, J. J. Kirkland and D. D. Bly, “Modern Size Exclusion Liquid Chromatography”, John Wiley and Sons, New York, 1979). Another useful method for determining molecular weight, particularly for lower molecular weight polymers, is vapor pressure osmometry (e.g., ASTM D3592).

The polyalkenyl moiety in a dispersant preferably has a narrow molecular weight distribution (MWD), also referred to as polydispersity, as determined by the ratio of weight average molecular weight (M_(w)) to number average molecular weight (M_(n)). Polymers having a M_(w)/M_(n) of less than 2.2, preferably less than 2.0, are most desirable. Suitable polymers have a polydispersity of from about 1.5 to 2.1, preferably from about 1.6 to about 1.8.

Suitable polyalkenes employed in the formation of the dispersants include homopolymers, interpolymers or lower molecular weight hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at least one C₃ to C₂ alpha-olefin having the formula H₂C═CHR¹ wherein R¹ is a straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein the polymer contains carbon-to-carbon unsaturation, and a high degree of terminal ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene and at least one alpha-olefin of the above formula, wherein R¹ is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms.

Another useful class of polymers is polymers prepared by cationic polymerization of monomers such as isobutene and styrene. Common polymers from this class include polyisobutenes obtained by polymerization of a C₄ refinery stream having a butene content of 35 to 75% by wt., and an isobutene content of 30 to 60% by wt. A preferred source of monomer for making poly-n-butenes is petroleum feedstreams such as Raffinate II. These feedstocks are disclosed in the art such as in U.S. Pat. No. 4,952,739. A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene olefins. Polyisobutene polymers that may be employed are generally based on a polymer chain of from 1500 to 3000.

The dispersant(s) are preferably non-polymeric (e.g., mono- or bis-succinimides). Such dispersants can be prepared by conventional processes such as disclosed in U.S. Patent Application Publication No. 2008/0020950, the disclosure of which is incorporated herein by reference.

The dispersant(s) can be borated by conventional means, as generally disclosed in U.S. Pat. Nos. 3,087,936, 3,254,025 and 5,430,105.

Such dispersants may be used in an amount of about 0.01 to 20 weight percent or 0.01 to 10 weight percent, preferably about 0.5 to 8 weight percent, or more preferably 0.5 to 4 weight percent. Or such dispersants may be used in an amount of about 2 to 12 weight percent, preferably about 4 to 10 weight percent, or more preferably 6 to 9 weight percent. On an active ingredient basis, such additives may be used in an amount of about 0.06 to 14 weight percent, preferably about 0.3 to 6 weight percent. The hydrocarbon portion of the dispersant atoms can range from C₆₀ to C₁₀₀₀, or from C₇₀ to C₃₀₀, or from C₇₀ to C₂₀₀. These dispersants may contain both neutral and basic nitrogen, and mixtures of both. Dispersants can be end-capped by borates and/or cyclic carbonates. Nitrogen content in the finished oil can vary from about 200 ppm by weight to about 2000 ppm by weight, preferably from about 200 ppm by weight to about 1200 ppm by weight. Basic nitrogen can vary from about 100 ppm by weight to about 1000 ppm by weight, preferably from about 100 ppm by weight to about 600 ppm by weight.

Dispersants as described herein are beneficially useful with the compositions of this disclosure and substitute for some or all of the surfactants of this disclosure. Further, in one embodiment, preparation of the compositions of this disclosure using one or more dispersants is achieved by combining ingredients of this disclosure, plus optional base stocks and lubricant additives, in a mixture at a temperature above the melting point of such ingredients, particularly that of the one or more M-carboxylates (M=H, metal, two or more metals, mixtures thereof).

As used herein, the dispersant concentrations are given on an “as delivered” basis. Typically, the active dispersant is delivered with a process oil. The “as delivered” dispersant typically contains from about 20 weight percent to about 80 weight percent, or from about 40 weight percent to about 60 weight percent, of active dispersant in the “as delivered” dispersant product.

Detergents

Illustrative detergents useful in this disclosure include, for example, alkali metal detergents, alkaline earth metal detergents, or mixtures of one or more alkali metal detergents and one or more alkaline earth metal detergents. A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur-containing acid, carboxylic acid (e.g., salicylic acid), phosphorus-containing acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal. The detergent can be overbased as described herein.

The detergent is preferably a metal salt of an organic or inorganic acid, a metal salt of a phenol, or mixtures thereof. The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. The organic or inorganic acid is selected from an aliphatic organic or inorganic acid, a cycloaliphatic organic or inorganic acid, an aromatic organic or inorganic acid, and mixtures thereof.

The metal is preferably selected from an alkali metal, an alkaline earth metal, and mixtures thereof. More preferably, the metal is selected from calcium (Ca), magnesium (Mg), and mixtures thereof.

The organic acid or inorganic acid is preferably selected from a sulfur-containing acid, a carboxylic acid, a phosphorus-containing acid, and mixtures thereof.

Preferably, the metal salt of an organic or inorganic acid or the metal salt of a phenol comprises calcium phenate, calcium sulfonate, calcium salicylate, magnesium phenate, magnesium sulfonate, magnesium salicylate, an overbased detergent, and mixtures thereof.

Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased. These detergents can be used in mixtures of neutral, overbased, highly overbased calcium salicylate, sulfonates, phenates and/or magnesium salicylate, sulfonates, phenates. The TBN ranges can vary from low, medium to high TBN products, including as low as 0 to as high as 600. Preferably the TBN delivered by the detergent is between 1 and 20. More preferably between 1 and 12. Mixtures of low, medium, high TBN can be used, along with mixtures of calcium and magnesium metal based detergents, and including sulfonates, phenates, salicylates, and carboxylates. A detergent mixture with a metal ratio of 1, in conjunction of a detergent with a metal ratio of 2, and as high as a detergent with a metal ratio of 5, can be used. Borated detergents can also be used.

Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀ or mixtures thereof. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched and can be used from 0.5 to 6 weight percent. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.

In accordance with this disclosure, metal salts of carboxylic acids are preferred detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula

where R is an alkyl group having 1 to about 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, barium, or mixtures thereof. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.

Alkaline earth metal phosphates are also used as detergents and are known in the art.

Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.

Preferred detergents include calcium sulfonates, magnesium sulfonates, calcium salicylates, magnesium salicylates, calcium phenates, magnesium phenates, and other related components (including borated detergents), and mixtures thereof. Preferred mixtures of detergents include magnesium sulfonate and calcium salicylate, magnesium sulfonate and calcium sulfonate, magnesium sulfonate and calcium phenate, calcium phenate and calcium salicylate, calcium phenate and calcium sulfonate, calcium phenate and magnesium salicylate, calcium phenate and magnesium phenate. Overbased detergents are also preferred.

The detergent concentration in the lubricating oils of this disclosure can range from about 0.5 to about 6.0 weight percent, preferably about 0.6 to 5.0 weight percent, and more preferably from about 0.8 weight percent to about 4.0 weight percent, based on the total weight of the lubricating oil.

As used herein, the detergent concentrations are given on an “as delivered” basis. Typically, the active detergent is delivered with a process oil. The “as delivered” detergent typically contains from about 20 weight percent to about 100 weight percent, or from about 40 weight percent to about 60 weight percent, of active detergent in the “as delivered” detergent product.

Antiwear Additives

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) can be a useful component of the lubricating oils of this disclosure. ZDDP can be derived from primary alcohols, secondary alcohols or mixtures thereof. ZDDP compounds generally are of the formula

Zn[SP(S)(OR¹)(OR²)]₂

where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched. Alcohols used in the ZDDP can be propanol, 2-propanol, butanol, secondary butanol, pentanols, hexanols such as 4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethyl hexanol, alkylated phenols, and the like. Mixtures of secondary alcohols or of primary and secondary alcohol can be preferred. Alkyl aryl groups may also be used.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from about 0.3 weight percent to about 1.5 weight percent, preferably from about 0.4 weight percent to about 1.2 weight percent, more preferably from about 0.5 weight percent to about 1.0 weight percent, and even more preferably from about 0.6 weight percent to about 0.8 weight percent, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a secondary ZDDP and present in an amount of from about 0.6 to 1.0 weight percent of the total weight of the lubricating oil.

Viscosity Modifiers

Viscosity modifiers (also known as viscosity index improvers (VI improvers), and viscosity improvers) can also be optionally included in the lubricant compositions of this disclosure. Advantageous viscosity modifiers for use in the lubricating oils disclosed herein, as discussed above, are of the polymeric type, also referred to as polymer thickening agents. Non-limiting exemplary polymer thickening agents are copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, polyacrylates and combinations thereof.

Viscosity modifiers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity modifiers include high molecular weight hydrocarbons, polyesters and viscosity modifier dispersants that function as both a viscosity modifier and a dispersant. Typical molecular weights of these polymers are between about 10,000 to 1,500,000, more typically about 20,000 to 1,200,000, and even more typically between about 50,000 and 1,000,000.

Examples of suitable viscosity modifiers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity modifier. Another suitable viscosity modifier is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity modifiers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 5850B”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Hydrogenated polyisoprene star polymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV200” and “SV600”. Hydrogenated diene-styrene block copolymers are commercially available from Infineum International Limited, e.g., under the trade designation “SV 50”.

The polymethacrylate or polyacrylate polymers can be linear polymers which are available from Evnoik Industries under the trade designation “Viscoplex®” (e.g., Viscoplex 6-954) or star polymers which are available from Lubrizol Corporation under the trade designation Asteric™ (e.g., Lubrizol 87708 and Lubrizol 87725).

Illustrative vinyl aromatic-containing polymers useful in this disclosure may be derived predominantly from vinyl aromatic hydrocarbon monomer. Illustrative vinyl aromatic-containing copolymers useful in this disclosure may be represented by the following general formula:

A-B

wherein A is a polymeric block derived predominantly from vinyl aromatic hydrocarbon monomer, and B is a polymeric block derived predominantly from conjugated diene monomer.

In an embodiment of this disclosure, the viscosity modifiers may be used in an amount of less than about 10 weight percent, preferably less than about 7 weight percent, more preferably less than about 4 weight percent, and in certain instances, may be used at less than 2 weight percent, preferably less than about 1 weight percent, and more preferably less than about 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil. Viscosity modifiers are typically added as concentrates, in large amounts of diluent oil.

As used herein, the viscosity modifier concentrations are given on an “as delivered” basis. Typically, the active polymer is delivered with a diluent oil. The “as delivered” viscosity modifier typically contains from 20 weight percent to 75 weight percent of an active polymer for polymethacrylate or polyacrylate polymers, or from 8 weight percent to 20 weight percent of an active polymer for olefin copolymers, hydrogenated polyisoprene star polymers, or hydrogenated diene-styrene block copolymers, in the “as delivered” polymer concentrate.

Antioxidants

Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.

Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C₆+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant disclosure. Examples of ortho-coupled phenols include: 2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol); and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4′-bis(2,6-di-t-butyl phenol) and 4,4′-methylene-bis(2,6-di-t-butyl phenol).

Effective amounts of one or more catalytic antioxidants may also be used. The catalytic antioxidants comprise an effective amount of a) one or more oil soluble polymetal organic compounds; and, effective amounts of b) one or more substituted N,N′-diaryl-o-phenylenediamine compounds or c) one or more hindered phenol compounds; or a combination of both b) and c). Catalytic antioxidants are more fully described in U.S. Pat. No. 8,048,833, herein incorporated by reference in its entirety.

Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)xR¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to about 20 carbon atoms, and preferably contains from about 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of at least about 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than about 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent, more preferably zero to less than 1.5 weight percent, more preferably zero to less than 1 weight percent.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of about 0.01 to 3 weight percent, preferably about 0.01 to 2 weight percent.

Antifoam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 weight percent and often less than 0.1 weight percent.

Inhibitors and Antirust Additives

Antirust additives (or corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. A wide variety of these are commercially available.

One type of antirust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of antirust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Yet another type of antirust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of about 0.01 to 5 weight percent, preferably about 0.01 to 1.5 weight percent.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure.

Illustrative friction modifiers may include, for example, organometallic compounds or materials, or mixtures thereof. Illustrative organometallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like, and mixtures thereof. Similar tungsten based compounds may be preferable.

Other illustrative friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, alkoxylated fatty acid esters, alkanolamides, polyol fatty acid esters, borated glycerol fatty acid esters, fatty alcohol ethers, and mixtures thereof.

Illustrative alkoxylated fatty acid esters include, for example, polyoxyethylene stearate, fatty acid polyglycol ester, and the like. These can include polyoxypropylene stearate, polyoxybutylene stearate, polyoxyethylene isosterate, polyoxypropylene isostearate, polyoxyethylene palmitate, and the like.

Illustrative alkanolamides include, for example, lauric acid diethylalkanolamide, palmic acid diethylalkanolamide, and the like. These can include oleic acid diethyalkanolamide, stearic acid diethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylated hydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.

Illustrative polyol fatty acid esters include, for example, glycerol mono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerol mono-stearate, and the like. These can include polyol esters, hydroxyl-containing polyol esters, and the like. Illustrative borated glycerol fatty acid esters include, for example, borated glycerol mono-oleate, borated saturated mono-, di-, and tri-glyceride esters, borated glycerol mono-sterate, and the like. In addition to glycerol polyols, these can include trimethylolpropane, pentaerythritol, sorbitan, and the like. These esters can be polyol monocarboxylate esters, polyol dicarboxylate esters, and on occasion polyoltricarboxylate esters. Preferred can be the glycerol mono-oleates, glycerol dioleates, glycerol trioleates, glycerol monostearates, glycerol distearates, and glycerol tristearates and the corresponding glycerol monopalmitates, glycerol dipalmitates, and glycerol tripalmitates, and the respective isostearates, linoleates, and the like. On occasion the glycerol esters can be preferred as well as mixtures containing any of these. Ethoxylated, propoxylated, butoxylated fatty acid esters of polyols, especially using glycerol as underlying polyol can be preferred.

Illustrative fatty alcohol ethers include, for example, stearyl ether, myristyl ether, and the like. Alcohols, including those that have carbon numbers from C₃ to C₅₀, can be ethoxylated, propoxylated, or butoxylated to form the corresponding fatty alkyl ethers. The underlying alcohol portion can preferably be stearyl, myristyl, C₁₁-C₁₃ hydrocarbon, oleyl, isosteryl, and the like.

The lubricating oils of this disclosure exhibit desired properties, e.g., wear control, in the presence or absence of a friction modifier.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 5 weight percent, or about 0.1 weight percent to about 2.5 weight percent, or about 0.1 weight percent to about 1.5 weight percent, or about 0.1 weight percent to about 1 weight percent. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 25 ppm to 700 ppm or more, and often with a preferred range of 50-200 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table 1 below.

It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. Accordingly, the weight amounts in the table below, as well as other amounts mentioned herein, are directed to the amount of active ingredient (that is the non-diluent portion of the ingredient). The weight percent (wt. %) indicated below is based on the total weight of the lubricating oil composition.

TABLE 1 Typical Amounts of Other Lubricating Oil Components Approximate Approximate Compound Wt. % (Useful) Wt. % (Preferred) Dispersant 0.1-20 0.1-8  Detergent 0.1-20 0.1-8  Friction Modifier 0.01-5   0.01-1.5 Antioxidant 0.1-5   0.1-1.5 Pour Point Depressant (PPD) 0.0-5  0.01-1.5 Anti-foam Agent 0.001-3   0.001-0.15 Viscosity Modifier (solid 0.1-2  0.1-1  polymer basis) Antiwear 0.2-3  0.5-1  Inhibitor and Antirust 0.01-5  0.01-1.5

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of lubricant oil additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The following non-limiting examples are provided to illustrate the disclosure.

Examples

Two liquid crystals (LC1 and LC2) as shown below were evaluated.

Liquid crystal 1 (LC1) was also evaluated as synthetic base stock and results are shown in FIG. 2. The liquid crystal of Example 1 (LC1) has extremely high viscosity index (VI). For example, PAO4 has VI of 126 while VI of LC is 342. A combination of DSC and rheology measurements were used to explain the high VI values measured. It has been discovered that there is an increase in viscosity with increase in temperature because of a nematic to isotropic transition in the liquid crystal. The liquid crystal LC 1 is soluble in Group IV base stock like polyalphaolefin (PAO) and Group V base stocks like alkylated naphthalene (AN) and esters. Such LCs can also be used as smart materials; for example, one may formulate LC based fluids whose viscosity is relatively insensitive to temperature.

Liquid crystals possess unique properties that have the potential to be harnessed in formulation of application-specific “smart” lubricants embodying usually conflicting properties (e.g. highly protective lubricant films with low traction and churning losses). Liquid crystals were shown to possess strong lubrication performance enhancements, including ultralow friction and low traction, compared to simple fluids. The DSC based phase transition in liquid crystal 1 and 2 coincides with rheology studies of the fluid (see later). The liquid crystal fluids disclosed herein allow of one to develop a multi-step phase transition fluid to achieve constant viscosity.

FIG. 1 shows illustrative liquid crystal base oil in accordance with the Example 1.

FIG. 2 shows viscosity and viscosity index (VI) of the liquid crystal base stock of Example 1. Note that viscosity index of the liquid crystal was very high. For comparison, polyalphaolefin PAO4 has VI of 126 while the VI of the liquid crystal of example 1 was 342. Such liquid crystal fluid allow for one to formulate an oil whose viscosity is relatively insensitive to temperature.

FIG. 3a show the DSC heating cycle for the L1 liquid crystal (Example 1). In the heating cycle, phase transitions occurred at 27.96° C. and 54° C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. FIG. 3b show the DSC cooling cycle for the L1 liquid crystal (Example 1).

FIG. 4 show the viscosity increases with temperature at around 52° C. This may be attributed to a nematic to isotropic phase transition in the liquid crystal. In the nematic phase, the molecules are aligned and hence slip past each other more easily upon application of shear. This leads to lower viscosity. Therefore, the viscosity between 52° C. and 64° C. is effectively constant with a small perturbation. This suggests that one may be able to develop a multi-step phase transition fluid to achieve constant viscosity as a function of temperature by formulating a fluid that is a combination of various liquid crystals undergoing the nematic to isotropic transitions at different temperatures.

FIG. 5 shows an illustrative liquid crystal base stock in accordance with the Example 2.

FIG. 6a shows the DSC heating curve for the liquid crystal (L2) of Example 2. In the heating cycle, phase transitions at 56.3 C and 66.4 C occurred. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The DSC cooling curve of FIG. 6b also reveals the existence of the liquid crystalline phase in this temperature range.

FIG. 7 presents viscosity as a function of temperature for the liquid crystal (L2) depicted above. Here, the temperature was changed in a decreasing manner. As expected, the viscosity initially increases with decreasing temperature. However, at 64° C., the viscosity drops, and then begins to rise steeply around 55° C. Note that this temperature range coincides with the range in which the material exists as a liquid crystalline phase based on the DSC data presented above in FIG. 6. The drop in viscosity was because of orientational alignment of the molecules of the material in the liquid crystalline phase. This alignment leads to lower collisions between molecules under shear and hence lower frictional losses and lower viscosity. The sharp increase in viscosity at temperatures lower than 55° C. is likely due to a phase transition to a glassy state or crystalline state. When we zoom into the liquid crystalline region, we see because of the drop in viscosity upon the transition to the liquid crystal phase, the material exhibited the same viscosity at 63° C. and 72° C. If the drop is small, this temperature range can be approximately modeled as having a constant viscosity. As a consequence, the viscosity index measured for the liquid crystal is very high as shown in FIG. 2.

In FIG. 8, the effect of shear on the alignment of molecules in the liquid crystal phase was examined. The red data shows viscosity vs. shear rate at 70° C. From DSC and rheology experiments, the material was in the isotropic phase at this temperature, and there was no shear thinning observed, as expected for an isotropic, purely viscous liquid with no long range interactions. When the same experiment was performed at 60° C., which is in the liquid crystalline region, we see that there was shear-thinning observed i.e. viscosity decreases with increasing shear rate. Shear-thinning usually occurs due to alignment of molecules; at low shear rates, the liquid crystal is in the nematic phase with loose orientation order which is imperfect. As the shear rate was increased, the flow further aligns molecules causing fewer molecular collisions and easier slippage of molecules past each other. The lower number of collisions led to lower viscosity at increased shear rate. In an isotropic fluid (such as at 70° C.), the orientation of molecules was too random for low shear rates to have any significant ability to align molecules.

To further confirm the presence of weak, long-range order in the liquid crystal state, we performed oscillatory shear measurements as shown in FIG. 9. Here, we applied sinusoidal deformations of increasing strain amplitude and measured the elastic (storage) and viscous (loss) moduli. For a fluid with no long-ranging interactions or orientational order, we expected to see a purely viscous response and zero elastic modulus. However, the data measured at 60° C. revealed non-zero elastic and viscous moduli. The finite elastic modulus measured shows the presence of long-range interactions in the fluid. As the strain amplitude was increased, long range interactions were progressively destroyed leading to a sharp decrease in the elastic modulus. However, the viscous modulus is relatively insensitive to the strain amplitude.

FIG. 10 shows illustrative liquid crystal base stocks in accordance with Examples 3-6.

FIG. 11 shows phase transition temperatures for the liquid crystals of Examples 1-6.

Phase Transitions: Rheology Coincides with DSC Measurements

Referring again to FIG. 3, the viscosity increases with temperature at around 52° C. This may be attributed to a nematic to isotropic phase transition in the LC. In the nematic phase, the molecules are aligned and hence slip past each other more easily upon application of shear. This leads to lower viscosity. Therefore, the viscosity between 52° C. and 64° C. is effectively constant with a small perturbation. This suggests that one may be able to develop a multi-step phase transition fluid to achieve constant viscosity as a function of temperature by formulating a fluid that is a combination of various LCs undergoing the nematic to isotropic transitions at different temperatures.

Referring again to FIG. 6, we show DSC data for the L2 liquid crystal (Example 2). In the heating cycle, we see a phase transitions at 56.3 C and 66.4 C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The cooling scan also revealed the existence of the liquid crystalline phase in this temperature range.

Referring again to FIG. 7, viscosity as a function of temperature for the L2 liquid crystal is shown. Here, the temperature was changed in a decreasing manner. As expected, the viscosity initially increased with decreasing temperature. However, at 64 C, the viscosity dropped, and then began to rise steeply at around 55° C. Note that this temperature range coincides with the range in which the material exists as a liquid crystalline phase based on the DSC data presented above. The drop in viscosity was because of orientational alignment of the molecules of the material in the liquid crystalline phase. This alignment led to lower collisions between molecules under shear, and hence lower frictional losses and lower viscosity. The sharp increase in viscosity at temperatures lower than 55° C. was likely due to a phase transition to a glassy state or crystalline state.

When we zoom into the liquid crystalline region, we see because of the drop in viscosity upon the transition to the LC phase, the material exhibited the same viscosity at 63° C. and 72° C. If the drop is small, this temperature range can be approximately modeled as having a constant viscosity. As a consequence, the VI measured for the LC was very high, as tabulated in FIG. 2.

Liquid Crystal Molecules Undergo Shear Induced Alignment in the Nematic Phase

Referring again to FIG. 8, we examined the effect of shear on the alignment of molecules in the liquid crystal phase. The red data shows viscosity vs. shear rate at 70° C. From DSC and rheology experiments, the material was in the isotropic phase at this temperature, and there was no shear thinning observed, as expected for an isotropic, purely viscous liquid with no long range interactions. When the same experiment was performed at 60 C, which is in the LC region, we saw that there is shear-thinning observed i.e. viscosity decreased with increasing shear rate. Shear-thinning usually occurs due to alignment of molecules; at low shear rates, the LC is in the nematic phase with loose orientation order which is imperfect. As the shear rate was increased, the flow further aligned molecules which causes fewer molecular collisions and easier slippage of molecules past each other. The lower number of collisions led to lower viscosity at increased shear-rate. In an isotropic fluid (such as at 70° C.), the orientation of molecules was too random for low shear rates to have any significant ability to align molecules.

To further confirm the presence of weak, long-range order in the LC state, we performed oscillatory shear measurements. Here, we applied sinusoidal deformations of increasing strain amplitude and measured the elastic (storage) and viscous (loss) moduli. For a fluid with no long-ranging interactions or orientational order, we expected to see a purely viscous response and zero elastic modulus. However, the data measured at 60 deg.C. revealed non-zero elastic and viscous moduli. The finite elastic modulus measured showed the presence of long-range interactions in the fluid. As the strain amplitude was increased, long range interactions were progressively destroyed leading to a sharp decrease in the elastic modulus. However, the viscous modulus was relatively insensitive to the strain amplitude.

The lubricating oil base stocks evaluated were liquid crystal base stocks depicted in FIGS. 1, 5 and 10.

Example 1. Liquid Crystal 4-((1 S,4r)-4-pentylcyclohexyl)benzonitrile as Base Stock

In the FIG. 2, we show viscosity data and in FIG. 3, we show DSC data for the L1 liquid crystal. In the heating cycle, we see a phase transitions at 27.96° C. and 54° C. The region between these two temperatures is the liquid crystalline region, where the material was still a liquid, yet has orientational order. The DSC cooling scan also revealed the existence of the liquid crystalline phase in this temperature range. The DSC cooling scan showed substantial super cooling.

Although the molecular weight of the liquid crystal was 255, it has a kinematic viscosity (Kv100) of 4.18 cSt. Surprisingly it was observed that the VI of the fluid was 342, exceptionally high for any fluid of such viscosity. The LC fluid was also soluble in PAO, AN and ester.

In FIG. 3, the viscosity increases with temperature at around 52° C. This may be attributed to a nematic to isotropic phase transition in the LC. In the nematic phase, the molecules are aligned and hence slip past each other more easily upon application of shear. This leads to lower viscosity. Therefore, the viscosity between 52° C. and 64° C. is effectively constant with a small perturbation. This suggests that one may be able to develop a multi-step phase transition fluid to achieve constant viscosity as a function of temperature by formulating a fluid that is a combination of various LCs undergoing the nematic to isotropic transitions at different temperatures.

Example 2. Liquid Crystal 4-pentylphenyl 4-(octyloxy) benzoate as Base Stock

Phase Transitions: Rheology Coincides with DSC Measurements

In FIG. 3, we show DSC data for the liquid crystal (Example 2). In the heating cycle, we see a phase transitions at 56.3 C and 66.4 C. The region between these two temperatures is the liquid crystalline region, where the material is still a liquid, yet has orientational order. The cooling scan also revealed the existence of the liquid crystalline phase in this temperature range.

In FIG. 4 presented is viscosity as a function of temperature for the L2 liquid crystal. Here, the temperature was changed in a decreasing manner. As expected, the viscosity initially increases with decreasing temperature. However, at 64 deg. C., the viscosity drops, and then begins to rise steeply around 55° C. Note that this temperature range coincides with the range in which the material exists as a liquid crystalline phase based on the DSC data presented above. The drop in viscosity is because of orientational alignment of the molecules of the material in the liquid crystalline phase. This alignment leads to lower collisions between molecules under shear, and hence lower frictional losses and lower viscosity. The sharp increase in viscosity at temperatures lower than 55° C. is likely due to a phase transition to a glassy state or crystalline state.

When we zoom into the liquid crystalline region, we see because of the drop in viscosity upon the transition to the LC phase, the material exhibits the same viscosity at 63° C. and 72° C. If the drop is small, this temperature range can be approximately modeled as having a constant viscosity. As a consequence, the VI measured for the LC is very large, as tabulated above.

Example 3. Synthesis of 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate (26892-015) LC3

4-heptylbenzoic acid (MW 220.31, 4.0 g, 18.16 mmol), 4-(hexyloxy)phenol (MW 194.27, 3.53 g, 18.16 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 3.75 g, 18.16 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.09 g, 0.73 mmol) were mixed in 40 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 5.21 g of white solid product. 111 NMR (CDCl₃, 400 MHz) δ 8.10 (dt, 2H, ArH), δ 7.30 (d, 2H, ArH), δ 7.10 and 6.92 (dt, dt, 2H, 2H, ArH), δ 3.96 (t, 2H, ArOCH₂—), δ 2.69 (t, 2H, ArCH₂—), δ 1.78 (quin, 2H, ArOCH₂CH₂—), δ 1.65 (quin, 2H, ArCH₂CH₂—), δ 1.47 (quin, 2H, ArOCH₂CH₂CH₂—), δ 1.40-1.22 (m, 12H, —CH₂—), δ 0.93-0.87 (t, t, 6H, CH₃—).

Example 4. Synthesis of 4-pentylphenyl 4-(heptyloxy)benzoate (26892-018) LC4

4-(heptyloxy)benzoic acid (MW 236.31, 4.0 g, 16.93 mmol), 4-pentylphenol (MW 164.24, 2.78 g, 16.93 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 3.49 g, 16.93 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.10 g, 0.85 mmol) were mixed in 60 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 4.36 g of white solid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.13 (dt, 2H, ArH), δ 7.21 (d, 2H, ArH), δ 7.09 and 6.96 (dt, dt, 2H, 2H, ArH), δ 4.04 (t, 2H, ArOCH₂—), δ 2.61 (t, 2H, ArCH₂—), δ 1.82 (quin, 2H, ArOCH₂CH₂—), δ 1.63 (quin, 2H, ArCH₂CH₂—), δ 1.47 (quin, 2H, ArOCH₂CH₂CH₂—), δ 1.41-1.27 (m, 10H, —CH₂—), δ 0.90 (t, 6H, CH₃—).

Example 5. Synthesis of 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate (26892-028) LC5

4-(heptyloxy)benzoic acid (MW 236.31, 6.0 g, 25.39 mmol), 4-(hexyloxy)phenol (MW 194.27, 6.93 g, 35.67 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 6.29 g, 30.47 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.31 g, 2.54 mmol) were mixed in 90 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 7.92 g of white solid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.12 (dt, 2H, ArH), δ 7.09 (dt, 2H, ArH), δ 6.97-6.90 (dt, dt, 4H, ArH), δ 4.03 and 3.95 (t, t, 2H, 2H, ArOCH₂—), δ 1.85-1.75 (m, 4H, ArOCH₂CH₂—), δ 1.51-1.42 (m, 4H, ArOCH₂CH₂CH₂—), δ 1.41-1.27 (m, 10H, —CH₂—), δ 0.93-0.88 (t, t, 6H, CH₃—). ¹³C NMR (CDCl₃, 100 MHz) δ 165.4, 163.6, 156.9, 144.5, 132.3, 122.6, 121.8, 115.2, 114.4, 68.5, 68.4, 31.9, 31.8, 29.4, 29.3, 29.2, 26.1, 25.9, 22.8, 14.23, 14.20.

Example 6. Synthesis of 4-pentylphenyl 4-heptylbenzoate (26892-030) LC6

4-heptylbenzoic acid (MW 220.31, 5.0 g, 22.69 mmol), 4-pentylphenol (MW 164.24, 5.6 g, 34.04 mmol), N,N′-dicyclohexylcarbodiimide (DCC) (MW 206.33, 5.62 g, 27.23 mmol), and 4-(dimethylamino)pyridine (DMAP) (MW 122.17, 0.28 g, 2.27 mmol) were mixed in 90 ml of methylene chloride (DCM) in a round bottom flask and stirred at room temperature overnight. The completion of the reaction was monitored by thin layer chromatography (TLC) using hexane/ethyl acetate as eluent. Then the reaction mixture was washed with 1N HCl, H₂O, 10% Na₂CO₃, H₂O, and brine; dried over MgSO₄, and concentrated under vacuum to give crude product, which was further purified by silica gel column chromatography to give 7.06 g of white milky liquid product. ¹H NMR (CDCl₃, 400 MHz) δ 8.10 (d, 2H, ArH), δ 7.30 (d, 2H, ArH), δ 7.21 and 7.10 (dt, dt, 2H, 2H, ArH), δ 2.69 and 2.61 (t, t, 2H, 2H, ArCH₂—), δ 1.69-1.58 (m, 4H, ArCH₂CH₂—), δ 1.40-1.22 (m, 12H, —CH₂—), δ 0.92-0.87 (t, t, 6H, CH₃—). ¹³C NMR (CDCl₃, 100 MHz) δ 165.5, 149.3, 149.1, 140.5, 130.4, 129.4, 128.7, 127.3, 121.5, 36.2, 35.5, 31.95, 31.6, 31.32, 31.31, 29.4, 29.3, 22.8, 22.7, 14.24, 14.2.

The LC fluids of the benzoate ester type provide one or more of the following advantages: low cost, no toxicity issues, improved viscosity temperature performance, and high viscosity index. The LC fluids of the benzoate ester type can also be used as PVC plasticizers.

PCT and EP Clauses:

1. A lubricant base stock comprising one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445.

2. The lubricant base stock of clause 1, wherein the one or more liquid crystals are represented by a formula selected from the group consisting of:

and combinations thereof.

3. The lubricant base stock of clause 1, wherein the one or more liquid crystals are selected from the group consisting of 4-((1s,4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate and combinations thereof.

4. The lubricant base stock of clauses 1-3, wherein the viscosity index of the lubricating oil base stock is greater than 300 at 100° C. as determined according to ASTM D-2270.

5. The lubricant base stock of clauses 1-4, wherein the one or more liquid crystals undergo a liquid crystal phase change at a temperature between −50° C. and 150° C. as measured by Differential Scanning calorimetry.

6. A lubricating oil comprising a lubricant base stock including one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH, or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally one or more viscosity modifiers.

7. The lubricating oil of clause 6, wherein the one or more liquid crystals are represented by a formula selected from the group consisting of:

and combinations thereof.

8. The lubricating oil of clause 6, wherein the one or more liquid crystals are selected from the group consisting of 4-((1s,4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate and combinations thereof.

9. The lubricating oil of clauses 6-8, wherein the viscosity index of the lubricating oil base stock is greater than 300 at 100° C. as determined according to ASTM D-2270.

10. The lubricating oil of clauses 6-9, wherein the one or more liquid crystals undergo a liquid crystal phase change at a temperature between −50° C. and 150° C. as measured by Differential Scanning calorimetry.

11. The lubricating oil of clauses 6-10, wherein the lubricant base stock comprises a major amount of the lubricating oil and the optional one or more viscosity modifiers comprises a minor amount of the lubricating oil.

12. The lubricating oil of clauses 6-11, wherein the lubricant base stock comprises from 50 to 99 wt % of the lubricating oil and the one or more viscosity modifiers comprises from 0.1 to 20 wt % of the lubricating oil.

13. The lubricating oil of clauses 6-12, wherein the viscosity modifier comprises a polymer thickening agent.

14. The lubricating oil of clause 13, wherein the polymer thickening agent is selected form the group consisting of copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, polyacrylates and combinations thereof.

15. The lubricating oil of clauses 6-14 further including from 1 to 45 wt % of a lubricant co-base stock, wherein the co-base stock is selected from the from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock and combinations thereof.

16. The lubricating oil of clauses 6-15 further including from 0.1 to 30 wt % of one or more other lubricating oil additives selected from the group consisting of an anti-wear additive, viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.

17. The lubricating oil of clauses 6-16, wherein the lubricating oil has a kinematic viscosity at 100 deg. C. ranging from 4.5 to 12.5 cSt.

18. The lubricating oil of clauses 6-17, wherein the viscosity index of the lubricating oil is greater than 200 at 100° C. as determined according to ASTM D-2270.

19. A method for improving viscosity temperature performance or viscosity index of a lubricating oil used in an engine or other mechanical component comprising the steps of: providing a lubricating oil as a formulated oil to an engine or other mechanical component, said formulated oil having a composition comprising at least one lubricating oil base stock including one or more liquid crystals represented by the formula:

R1-(A)_(m)-Y—(B)_(n)—R2

wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally one or more viscosity modifiers; and measuring viscosity temperature performance or viscosity index of the engine or other mechanical component lubricated with the lubricating oil; and wherein the viscosity temperature performance or viscosity index is improved as compared to viscosity temperature performance or viscosity index achieved using a comparable lubricating oil not including the lubricating oil base stock comprising the one or more liquid crystals.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

1. A lubricant base stock comprising one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH, or —C≡N; and m and n are independently 0, 1, 2 or 3; and wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445.
 2. The lubricant base stock of claim 1, wherein the one or more liquid crystals are represented by a formula selected from the group consisting of:

and combinations thereof.
 3. The lubricant base stock of claim 1, wherein the one or more liquid crystals are selected from the group consisting of 4-((1s, 4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate and combinations thereof.
 4. The lubricant base stock of claim 1, wherein the viscosity index of the lubricating oil base stock is greater than 300 at 100° C. as determined according to ASTM D-2270.
 5. The lubricant base stock of claim 1, wherein the one or more liquid crystals undergo a liquid crystal phase change at a temperature between −50° C. and 150° C. as measured by Differential Scanning calorimetry.
 6. A lubricating oil comprising a lubricant base stock including one or more liquid crystals, wherein the one or more liquid crystals are represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH, or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally one or more viscosity modifiers.
 7. The lubricating oil of claim 6, wherein the one or more liquid crystals are represented by a formula selected from the group consisting of:

and combinations thereof.
 8. The lubricating oil of claim 6, wherein the one or more liquid crystals are selected from the group consisting of 4-((1s, 4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate and combinations thereof.
 9. The lubricating oil of claim 6, wherein the viscosity index of the lubricating oil base stock is greater than 300 at 100° C. as determined according to ASTM D-2270.
 10. The lubricating oil of claim 6, wherein the one or more liquid crystals undergo a liquid crystal phase change at a temperature between −50° C. and 150° C. as measured by Differential Scanning calorimetry.
 11. The lubricating oil of claim 6, wherein the lubricant base stock comprises a major amount of the lubricating oil and the optional one or more viscosity modifiers comprises a minor amount of the lubricating oil.
 12. The lubricating oil of claim 11, wherein the lubricant base stock comprises from 50 to 99 wt % of the lubricating oil and the one or more viscosity modifiers comprises from 0.1 to 20 wt % of the lubricating oil.
 13. The lubricating oil of claim 6, wherein the viscosity modifier comprises a polymer thickening agent.
 14. The lubricating oil of claim 13, wherein the polymer thickening agent is selected form the group consisting of copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, polyacrylates and combinations thereof.
 15. The lubricating oil of claim 12 further including from 1 to 45 wt % of a lubricant co-base stock, wherein the co-base stock is selected from the from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock and combinations thereof.
 16. The lubricating oil of claim 12 further including from 0.1 to 30 wt % of one or more other lubricating oil additives selected from the group consisting of an anti-wear additive, viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.
 17. The lubricating oil of claim 6, wherein the lubricating oil has a kinematic viscosity at 100 deg. C. ranging from 4.5 to 12.5 cSt.
 18. The lubricating oil of claim 6, wherein the viscosity index of the lubricating oil is greater than 200 at 100° C. as determined according to ASTM D-2270.
 19. The lubricating oil of claim 6, wherein lubricating oil is an SAE viscosity grade selected from the group consisting of 0W-30, 5W-30, 0W-20, 5W-20, 0W-16, 5W-16, 0W-12, 5W-12, 0W-8, and 5W-8.
 20. The lubricating oil of claim 6, wherein the lubricating oil is a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO).
 21. A method for improving viscosity temperature performance or viscosity index of a lubricating oil used in an engine or other mechanical component comprising the steps of: providing a lubricating oil as a formulated oil to an engine or other mechanical component, said formulated oil having a composition comprising at least one lubricating oil base stock including one or more liquid crystals represented by the formula: R1-(A)_(m)-Y—(B)_(n)—R2 wherein R1 and R2 are the same or different and are a substituted or unsubstituted, alkyl or alkoxy group having from about 0 to about 24 carbon atoms; A and B are the same or different and are a cycloaliphatic group or aromatic group, provided at least one of A and B is an aromatic group; Y is a covalent bond, —CH₂—CH₂—, —CH═CH—, —OCOO—, —COO—, —CO—, —CSO—, —CSS—, —CS—, —O—, —S—, —SO—, —SO₂—, —CH₂O—, —OCH₂O—, —NO—, —ONO₂, COOH, OH or —C≡N; and m and n are independently 0, 1, 2 or 3; wherein the lubricant base stock has a kinematic viscosity of 2 cSt to 28 cSt at 40° C. and a kinematic viscosity of 1 cSt to 12 cSt at 100° C., as determined according to ASTM D445; and optionally one or more viscosity modifiers; and measuring viscosity temperature performance or viscosity index of the engine or other mechanical component lubricated with the lubricating oil; and wherein the viscosity temperature performance or viscosity index is improved as compared to viscosity temperature performance or viscosity index achieved using a comparable lubricating oil not including the lubricating oil base stock comprising the one or more liquid crystals.
 22. The method of claim 21, wherein the one or more liquid crystals are represented by the formula:

and combinations thereof.
 23. The method of claim 21, wherein the one or more liquid crystals are selected from the group consisting of 4-((1s,4r)-4-pentylcyclohexyl)benzonitrile, 4-pentylphenyl 4-(octylocy)benzoate 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-(heptyloxy)benzoate, 4-(hexyloxy)phenyl 4-(heptyloxy)benzoate, 4-pentylphenyl 4-heptylbenzoate and combinations thereof.
 24. The method of claim 21, wherein the viscosity index of the lubricating oil base stock is greater than 300 at 100° C. as determined according to ASTM D-2270.
 25. The method of claim 21, wherein the one or more liquid crystals undergo a liquid crystal phase change at a temperature between −50° C. and 150° C. as measured by Differential Scanning calorimetry.
 26. The method of claim 21, wherein the lubricant base stock comprises a major amount of the lubricating oil and the optional one or more viscosity modifiers comprises a minor amount of the lubricating oil.
 27. The method of claim 26, wherein the lubricant base stock comprises from 50 to 99 wt % of the lubricating oil and the one or more viscosity modifiers comprises from 0.1 to 20 wt % of the lubricating oil.
 28. The method of claim 21, wherein the viscosity modifier comprises a polymer thickening agent.
 29. The method of claim 28, wherein the polymer thickening agent is selected form the group consisting of copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, polyacrylates and combinations thereof.
 30. The method of claim 27 further including from 1 to 45 wt % of a lubricant co-base stock, wherein the co-base stock is selected from the from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock and combinations thereof.
 31. The method of claim 27 further including from 0.1 to 30 wt % of one or more other lubricating oil additives selected from the group consisting of an anti-wear additive, viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.
 32. The method of claim 21, wherein the lubricating oil has a kinematic viscosity at 100 deg. C. ranging from 4.5 to 12.5 cSt.
 33. The method of claim 21, wherein the viscosity index of the lubricating oil is greater than 200 at 100° C. as determined according to ASTM D-2270.
 34. The method of claim 21, wherein lubricating oil is an SAE viscosity grade selected from the group consisting of 0W-30, 5W-30, 0W-20, 5W-20, 0W-16, 5W-16, 0W-12, 5W-12, 0W-8, and 5W-8.
 35. The method oil of claim 21, wherein the lubricating oil is a passenger vehicle engine oil (PVEO) or a commercial vehicle engine oil (CVEO).
 36. The method of claim 21, wherein the other mechanical component is selected from the group consisting of an electric vehicle component, power train, a driveline, a transmission, a gear, a gear train, a gear set, a compressor, a pump, a hydraulic system, a bearing, a bushing, a turbine, a piston, a piston ring, a cylinder liner, a cylinder, a cam, a tappet, a lifter, a gear, a valve, or a bearing including a journal, a roller, a tapered, a needle, and a ball bearing. 